This invention relates to a ceramic cutting tip which is applicable to a cutting tool of a lathe, a milling machine and the like.
In the following, the term ceramic cutting tip shall be understood to mean a cutting tip formed of a so-called self-bonded sintered body whose crystalline particles are directly bonded with each other. A typical ceramic cutting tip contains highly pure alumina and alumina-carbide, for example, Al.sub.2 O.sub.3 --TiC. On the contrary, in a cutting tip formed of so-called extra-hard alloy or cermet, crystalline particles are bonded together through bonding metals such as iron, chromium, nickel and the like.
In the following Table 1 are shown compositions, hardness and traverse bending strengths of the ceramic cutting tip, extra-hard alloy cutting tip and cermet cutting tip.
Table 1 ______________________________________ Traverse bending Kind of Hardness Strength chip Composition (HRA) (kg/mm.sup.2) ______________________________________ Highly pure Ceramic Alumina 93-94 30-50 cutting tip Al.sub.2 O.sub.3 -carbide 93.5-94.5 60-80 Extra-hard alloy WC-bonding 90- 92 140- 200 cutting tip metal Cermet TiC-bonding 91- 92 100- 150 cutting tip metal ______________________________________
As seen from the above Table 1, the ceramic cutting tip is superior in hardness to the extra-hard alloy cutting tip and the cermet cutting tip, but inferior in traverse bending strength to the latter two and hence is brittle. That is, the ceramic cutting tip has an excellent wear resistance and hence is applicable to a cutting tool of a lathe, a milling machine and the like. However, the ceramic cutting tip has the disadvantage that there is a risk of the tip being easily damaged when it is brought into contact with another body or by the shock due to dropping produced when the tip is transported or packed or mounted on a cutting machine, and as a result, the ceramic cutting tip is difficult in handling.